Exciton dynamics and logic operations in a near-field optically coupled quantum-dot system

High spatial localization of an optical near field allows us to access and excite individual nanometric materials that are much smaller than the diffraction limit of light, while propagating or far-field light can only excite the system globally. This difference, as an initial condition, provides the new exciton dynamics by effective use of a dark state, or a dipole-forbidden state in a quantum-dot (QD) system coupled by the optical near field. We show theoretically and experimentally excitation energy transfer between CuCl quantum cubes, using temporally and spatially resolved near-field spectroscopy. In addition, we report another new feature of the exciton dynamics inherent in a similar system, or characteristic functional (AND/XOR-logic) operations, depending on the initial excitation as well as symmetry of the spatial arrangement of the QDs. (c) 2004 Elsevier B.V. All rights reserved.